Hi Frank,
I only want to note that the default is bilinear interpolation of the DEM.
Part of the code: const char *pszDEMInterpolation =
CSLFetchNameValueDef( papszOptions, "RPC_DEMINTERPOLATION", "bilinear" );
Best regards,
Dmitriy
16.01.2013 22:47, Frank Warmerdam ?????:
Yehiyam,
I do not see why you think the AREA_OR_POINT value ought to have any
influence on how DEM values are interpolated.
Note that a PixelIsPoint GeoTIFF file will already result in a GDAL
GeoTransform that is offset by half a pixel. The GDAL GeoTransform
always treats pixels as areas, and GDAL interpolators - presumably
including the for RPCs - should treat the pixel value as being at the
center of the pixel area for the purpose of interpolation (regardless
of whether that value is point or area).
On the other hand, I am denying the possibility that the RPC DEM
interpolation is always off by half a pixel. I haven't actually
looked closely at that code lately and the RPC code is not so very
well tested and validated.
Best regards,
Frank
On Wed, Jan 16, 2013 at 4:40 AM, Livneh Yehiyam <ye...@rafael.co.il
<mailto:ye...@rafael.co.il>> wrote:
Hi
I have a question about the RPC transform implemented in gdal_rpc.cpp.
If a dem file is specified in the transform options (RPC_DEM) the
file is sampled to retrieve the elevation of the transformed point.
In the case where the dem file is a DTED file (which defines
AREA_OR_POINT to POINT), shouldn't the pixel/line values in the
dem file be offset by half a pixel to get the correct height?
Thanks
Yehiyam
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